Mercury switch



H. L. LAMBERT 2,333,533

MERCURY SWITCH yFiled July 27, v1942 /l TTONEYS Patente'dlNov. 2,l 1943 MERCURY SWITCH Harry L. Lambert, Enlield, N. Y., assignor to Allen Wales Adding Machine Corporation, Ithaca,

Application July 27, 1942, Serial No. 452,405

(Cl. 20o-80) A12 Claims.

This invention relates to electric switches and particularly to the type known as mercury tube switches. Switches of this type are useful to control 'a circuit for any purpose, an... to control the speed of a rotatingelement by controlling the circuit of the driving motor,k as for example, in calculating machines where such machines are often placed, by their users on different surfaces which vary from a level condition to quite a substantial extent. It has been found that when such switches as heretofore made, are operated by centrifugal forces developed by rotation of an element, the speed at winch. the switch will be operated will be different when the machine is in different positions, such as when the machine is resting upon vsurfaces having different inclinations.

The present application isin-the nature of an improvement upon the mercury-switches disclosed and claimed in my prior applications, vSerial Nos. 296,124 and 420,507, the latter being now Patent N o. 2,301,217 of November 10, 1942. The switches of those prior applications led September 22,

1939, and November 26, 1941, respectively, utilize a globule of mercury which makes or breaks a cir- /cu'it by changes in the shape of the globule against the action of its surface tension, while the globule rests on a surface which it does-not Wet and remains undivided and in the same relative position on the surface during its distortion or change of shape.

Mercury tube switches as heretofore made also have been relatively expensive and required special mountings and skilled labor in order to enableA replacementof the switches, if they'became broken or inactive 'for any purpose.

An object of this invention is to improve and lsimplify mercury switches of the type utilizing a globule of mercury as the medium which makes and breaks the circuit, which may be replaced in the same simple manner employed to replace an electric light bulb in a socket included in the circuit to be controlled, which switch will be small and compact, which will be protected against breakage, as much as possible, which may be easily exhausted and its .chamber for the mercury filled with an inert g'as in a simple manner, and which will be relatively simple, compact, durable and' inexpensive.

Another object of the invention is to provide an improved mercury globule type of switch in which the globule, by changes in its shape against the forces of surface tension and while it remains undivided, will change the conducting condition of a circuit in which it is included, at the samecuit to be controlled thereby when aselected speed is obtained, irrespective of the inclination of the surface on which such `device is supported.

Various other objects and advantages will be apparent from the following description of several embodimentsof the invention, and the novel Y features will be particularly pointed out hereinafter in connection with the appended claims.

In the accompanying drawing:

Fig. 1 is aside elevation ofa rotating element, with a portion shown in section, having thereon a circuit controller constructed in accordance with this invention;

Fig. 2 is a transverse sectional elevation of the same, the section being taken approximately along the line 2-2 of Fig. 1;

Fig. 3 is a longitudinal sectional elevation through a mercury tube switch representing one embodiment of the invention;

Fig. 4 is a tranverse sectional elevation through the same, the section being taken approximately along the line 4 4 of Fig. 3;

-Fig' 5 is a longitudinal sectional elevation through a switch, also constructed in accordance with the invention, and similar to the embodiment shown in Figs. 3 and 4, but illustrating a slight modification thereof;

Fig. 6 is a similar longitudinal sectional elevation through a mercury tube switch also constructed in accordance with the invention, but

illustrating still another embodiment of the invention;

Figs. 7 to 10 are diagrams illustrating how the switch when the switch is in a plurality of dller ent positions, and by the dash lines, how the mer cury globule moves into an effective position to control the circuit in which it is included at the same speed, regardless of the inclination to the horizontal in which the axis of the tube is placed;

and

Figs. 11 and 12V are longitudinal and cross sectional elevations respectively of mercury switches which may also utilize some features of the invention.

4Referring flrst to Figs. 1 to 4, the shaft -I may be the shaft of a motor, or a shaft driven by a motor through a suitable gear reduction mechv anism, or just a rotating shaft. The improved circuit controller is mounted on the shaft I, and

centric to the axis of rotation of the shaft I, and

a base 6 is disposed in the eccentric recess 5. The recess is, of course, circular in shape and the base 6 has a circular periphery so that fit may be rotated iri the recess 5. Straps 1 are secured to the outer face of member 2 in any suitable manner, such as by screws 6, and overlie the outer face of the base 6 so as to confine the latter within the recess 5 while permitting rotation of the base 6 in the recess 5. By tightening the screws 8, the friction of the straps 1 on the base 6 may be varied, so that after the base 6 has been rotated into any selected position in the recess 5, a tightening of the screws 8 will clamp the base 6 in that adjusted position and cause it to rotate as a unit with the base element 2.

Mounted on the exposed end face of the base 6 is a socket element 9 of any suitable construction, such as of the type employed in automobile lights for removably mounting the electric light bulbs, This socket element 9 is mounted on the base 6 eccentrically of the periphery of thatbase, as shown in Fig. 2, so that when the base 6 is rotated in the recess 5, the socket element'l 9 will be shifted into positions having different shaft I An improved mercury tube switch A (Figs. 1y

and 2) is mounted removably in the socket element 9, and for this purpose, the switch A has a metal sleeve or ferrule I on its base, which ferrule is telescopically received in the cavity of the socket element 9 and has a pin II projecting radially therefrom so as to be received in a bayonet slot I2 in the side wall of socket element 9. When the switch A is inserted in the socket element 9, the pin II is first placed in alinement with the entrance end of the slot I2, the switch element then moved endwise into the socket element 9, and then it is given a'turn so as to carry the pin II into the offset end of the bayonet slot I2 and lock the switch A release-bly in the socket element 9. The opposite face of the member 2 carries collector rings I3 and I4, circular in character and approximately'concentric with the shaft I, and formed of metal or other electricity conducting material. Brushes .I and I6 are suitably mounted on a support Il so as to bear upon the collector rings I3 and I4v respectively as the latter rotates with the shaft I The brushes are insulated from the support I1, and for this purpose, the latter may be made of insulating material; and the brushes are electrically connected to circuit wires I8 and I9. A wire leads from the collector ring I4 to the sidewall or tubular part of the socket element 9 which is of metal, and a wire 2Iy connects the vcollector ring I3 to a' central yielding' contact 22 in the bottom of the socket element as usual in this type of socket, and which contact 22 is engaged by a central terminal or contact on the end of the switch A.

In Figs. 3. and 4, one embodiment ot the improved switch tube 'is illustrated, and this switch in the form ,here shown, includes a hollow, somewhat spherical, cup-like casing -23 of a metal not wet by mercury, or at least having on its inner face a metal coating not wet by mercury. This casing has an opening at one side or end, with a cylindrical flange 424 around that opening. A wall 25 of glass is applied, while plastic, to the flange 24 so as to receive intended therein the ilange 24. The glass forms a seal with the flange 24 and closes the opening. The glass 25 and the metal casing 23 are chosen so as to have approximately the same coefllcient of thermal expansion. A common metal not wet by mercury and which is frequently used in the manufacture of mercury switches is iron alone or in alloy form. One form of metal not wet by mercury, and which has a coeflicient of thermal expansion approximately that of glass is available in the open market under the tr'ade name of \Kovar, and glass suitable for this purpose which has approximately the same coefcient of thermal expansion as the Kovar metal is available in the open market. The glass wll 25 as applied to the flange 24, has a small, tubelike extension 26, anclafter the glass wall 25 has been sealed to the flange 24, a globule of mercury may be inserted through this tube 26 into the chamber of the casing 23, the atmosphere of the casing chamber exhausted, and an inert gas inserted into the chamber so as to prevent deterioration of the mercury and contact surfaces within the chamber when making and breaking a circuit. The tube 26 is then fused or drawn so as to close it, as usual in the manufacture of light bulbs and glass mercury tube switches. This fused and drawn tube 26 is shown in Fig. 3 as extending outwardly from the outer face of the glass wall 25.

A conductor 21 which is also of a metal having approximately the same rate of expansion as glass, passes through the glass wall 25 approximately centrally thereof, and the end of this conductor 21 which is within the chamber of the casing 23 terminates in a head 28 whose surface is everywhere equidistant from the inner surface of the casing 23. When the chamber of casing 23 has the curvature of a sphere, the head 28 will be spherical and concentric thereto. The diameter of the head 28 is suiciently small to enable it to be passed through the opening surrounded by the iiange 24, jand the element 21 is preferably passed through the glass wall before that glass wall is applied to the flange 24. conductor 21 is so placed in the glass wall that the head 28 will be approximately concentric with the wall of the casing 23 which defines the chamber.

Within the chamber of the casing 23 is a globule 29 of mercury or of any other electrically conducting liquid having a strong surface tension. Mercury is the conducting liquid most commonly employed for this purpose, because of its exceptionally high surface tension. This globule of -mercury is of asize which only partially i'llls the chamber in the casing 23, and when resting on the wall of the casing 23 will contact the head 26, as shown clearly in Figs. 3 and 4; This globule 'of mercury thus forms an electrical connection between the casing 23 and the head 26. Th'e mercury globule is also of a size to assume a curved form in which a substantial .portion thereof is held away from and againstlspreading along the chamber wall of casing 23 solely by its surface tension in opposition to gravity,

The..

tion or another in the casing chamber.

and such a mass of mercury when resting on a surface which it does not wet usually assumes -a somewhat ball-like form which may be distorted or flattened somewhat, depending upon the action of gravity on the mass of the mercury forming the globule, and which flattening obviously becomes greater progressively as the size of the globule increases.

The metal sleeve I telescopes over the glass wall 25, abuts against the casing 23, and maybe electrically connected to the casing 23 in any suitable manner, such as by a drop 30 of solder or welding material. This tube I0 is in the nature of a metallic sleeve which thus projects away from the casing 23 and past the wall 25,`so as to protect the latter vand the fused tube tip 28. The conductor 21 extends approximately to the end of the sleeve II) where it terminates in a contact head or button 3|. The outer end of the sleeve III is closed by a disk or button 32 of insulating material through which the conductor 21 extends and against the face of which the head 3I` abuts. The space within the sleeve IU l between the disk 32 and the glass wall 25 is filled with a suitable insulating material 33, and it may be a filling similar to the fillings commonly employed in electric incandescent lamps, or it may be any insulating pitch or plastic material which is applied, while it is plastic, to the interior of the sleeve Il). ing material may extend past the periphery of the glass wall 25 so as to form a liner lfor the sleeve I0 and prevent metal to glass contact between the sleeve II) and the glass wall 25. This sleeve III carries the bayonet joint pin II.

In this embodiment of' the invention, the glass wall 25 has an integral projection 3l which surrounds the conductor 21 to the spherical head 28, so that the globule of mercury can only make contact between the easingv 23 and the conductor 21 through the head 28 and not by direct contact of the globule of mercury with the conductor rod -21 beyond the head 28. It will be noted that the radial distance from the periphery of the head 28 to the periphery of the chamber in the casing 23 will be substantially equal everywhere around the head 28, and therefore, no matter where the globule of mercury 29 is disposed in the chamber of the casing 23, it will' electrically connect -the head 28 and the casing 23 and the same degree of flattening of the globule of mercury will be necessary to open the circuitl between the casing 23 and the head 28,

whether the mercury globule 29 is in one posi- Thus when the switch shown in Figs. 3 and 4 is mount- If desired., this insulat-- f airand refilled with an inert. gas.

reached some particular speed, the attening of the mercury globule will be sufficient to -break .contact between it and the head 28, as ,shown by dotted lines in Figs. 3-9 and .11, and thus open the circuit between the circuit wires I8 and I9. The circuit wires I8 and I9 may control a signal which indicates by the breaking of the circuit that a particular speed has been reached or exceeded, or' the circuit wires I8 and I9 may be in series with the motor driving the shaft I, so as toact as a governor therefore, or the wires I8 and I9 may be in a relay circuit which controls the circuit for the motor which drives the shaft' I. 4

When the wires I8 and I9 control the motor, then the mercury tube switch acts as a governor for the speed of the motor and holds the speed to a particular speed. By rotating the base 8 in the recess 5, this switch tube may be shifted toward and from the axis of rotation, so as to determine the speed at which the mercury globule opens the circuit between the wires I8 and I9.-

I9 will be broken because, if the globule of mercury 29 is larger, a greater degree of flattening of the globule will be necessary before lt will leave contact with the head 28.

rl'he embodiment of the invention shown in Fig. 5 is the same as that shown in Figs. 3 and 4, except that the projection 34 on the glass wall 25 has been omitted, and otherwise corresponding parts are designated by corresponding reference characters. l

In Fig. 6 another embodiment of the invention is illustrated, in which the casing 35 is made of glass similar to that of `the glass Wall 25 in Figs. 3 to 5, and this glass casing 35 is provided with a generally spherical chamber 36. The casing 35 has -a relatively thicker wall 31`at one side ,with a. capillary tube 38 similar to the part 2B in Figs. 3 and 4, through which mercury may be inserted and the chamber 36 in the casing exhausted of The capillary tube is then sealed inthe .manner that electric light bulbs and glass tube mercury switches are sealed. A conductor rod 21, similar to the rod 21 of Figs. 3 to 5, extends through they wall 31 and into the chamber 36 of the casing 35 and there terminates in a spherical head 28. The rod 21 and head 28 are, of course, made of metal not wet by mercury, preferably one such as Kovar hereinabove referred to and which has approxied in the socket element 9, as shown in Figs. 1 y

and 2, the mercury will form an electrical con-v nection between the circuit wiresl I8 and I9.v

It will be noted also that in this form of the invention, the longitudinal axis of the switch which, in the form shown in Figs. 3 and 4 is approximately coincident with the conductor 21, -will be disposed parallel to the axis of the shaft I, but at one side of and parallel thereto. Thus when the shaft I rotates, the globule 29 will move into the zoneof the surface dening the chamber of casing 23, which is farthest from theaxls of rotationI and it will remain in that position undivided and relatively immovable thereon throughout such rotation and in all variations of speed. As the speed'of rotation of the switch tube increases, centrifugal forces tend to flatten the globule against the action of its surface tension, and when the speed has mately the same coeiiicient of thermal expansion as that of which the glass of the casing 35 andy wall 31. is made. Received over a shoulder on the wall 31. is the metal sleeve I0 corresponding to the sleeve II) of Figs. l to 5,.

A conductor 39 also extends through the wall 31 in spaced relation to the rod 21 and thepor'- tion of that conductor within the chamber of the casing 35 is threaded somewhat spirally across the chamber 36 in contact with the inner peripheral wall of the casing, and with the turns 4|! thereof spaced somewhat from one another, as shown in Fig. 6'. The outer end of the' conductor 39 extends along within the sleeve I0 and is electrically and mechanically connected to the free of the sleeve, in this embodiment of the inven-` tion, is also fllled with a suitable filler 4I, similar to the ller 33 of Figs. 1 to 5. A globule 29 of mercury is. also placed in the chamber 38 so as' to normally contact; the spherical head 28. The turns 48 of the conductor 39 are sumciently close together so that the mercury globule will always contact with at least oneof the turns Il in every position around the interior of the casing 35, into whichthe globule may move as the casing is tilted into different positions.

Since lthe turns 'l0 of the conductor are spaced from the spherical head 28- the globule will normally connect the conductor 39 tothe head 28 in all positions in which the casing 35 may be placed, but ii' the casing is rotated, such as about an axis generally parallel vto but offset from the axis of the rod 21 or the axis of the sleeve I8, the globule of mercury will move into a position on the portion of the inner wall-of the casing 35, which is farthest from the axis of rotation, and when ilattened by centrifugal forces. will leave contact with the head 28, and thus open the circuit between the head 28 and conductor 39. The portion of conductor 39 which passes` through wall 31 is also preferably made of Kovar metal or similar metal, and the portion within the chamber is either of the same material or some material,`such as iron, which is not wet by mercury.

In Figs. '7 to 9, I have illustrated diagrammati- `cally the position of the globule of mercury in the casing 23, when the casing is supported in different inclined positions. For example, in Fig. '1, the switch is supported in an upright position in which the rod 21 extends vertically, and the globule 29 of mercury settles to the bottom, as

` shown by full lines in Fig. '1, where it electricallyv great enough to ilatten the globule and cause it to I open the circuit. It will be noted, however, that the globule 28 normally closes the circuit between the conductor rod 21 and the casing 23, even though the switch extends upwardly.

In Fig. 8 a switch disposed at an acute angle to the horizontal is shown, that is, tipped sidewise from the position shown in Fig. 7, and the mercury globule 29 still connects the casing 23 tothe head 28, but if the switch is rotated about an axis parallel to but at one side of the conductor rod 21, the globule of mercury will move into a. relative position that is approximately the same as shown in Fig. 7, by the dash line, but if the switch is rotated about an axis, such as shown by the dot and dash line B-B in Fig. 8, then the globule of mercury will move into the dash line position shown in Fig. 8, and will function to open and close the circuit in the manner explained in connection with Fig. '1.

In Fig. 9, the same switch is disposed so as to depend from its support, and the globule of mercury will settle to the end which is then lowermoet, as shown by full lines in Fig. 9 and connect the casing and head, and if the tube is then rotated about an axis parallel to b'ut at the right ot the rod 21 in Fig. 9, the mercury globule will move into they position shown by dash lines inV ner las explained for Figs. 1 to 9, irrespective of the inclination or position of the switch.

It will be noted that the circuit between the wires 28 and 2| will be closed in any position of the switch and in any inclination, and as soon as the operation starts, the mercury globule will move while still connecting wires 20 and 2l into its expected position on the casing Wall portion which is then farthest from the axis of rotation.

In Figs. 1l and 12, certain Ieaturesof this invention are shown as having been incorporated in 'still another embodiment. In this form, the casing 23a, instead of being generally spherical, as in Figs. 1 to 5, is made cylindrical and of Kovar metal or other electrically conducting material not wet by mercury. Both ends of this sleeve are then closed by glass plates 25a and 25h, which are similar to the plate 25 of Figs. 1 to 5. The conductor rod 21 which corresponds to the conductor rod 21 of Figs. l to 5, after extending through one end Wall 25h, continues across the chamber of 'the casing of the sleeve 23a and is slidingly received iny a recess in the inner face of the end wall 25a. This provides a closed casing with the glass end walls, and this glass of the same material as glass wall 25, has approximately the same coefficient of thermal expansion as the metal, so that a tight seal is obtained. The globule 29 of mercury is also inserted in the chamber of this sleeve 23a so as t9 contact with the periphery of the conductor rods 21.

Theferrule I8 lits over the end wall 25h as in the other forms of the invention, and the connector rod 21 extends to the end of the sleeve and terminates in the head 3l, the same as in Figs. 1 to 6.. The mercury and inert gas may be inserted through a capillarytube extension in the end wall 25h, the same as explained for the wall `25 of Figs. l to 5, and the sleeve i0 may be connected to the sleeve 23a forming the casing by a small drop of solder or welding material 30a. It will be noted that in this form of the invention, the conductor rod 21 is also everywhere equldistant from the sleeve 23a and the switch is also a unit which can be handled like an electriclight bulb to connect-or .disconnect it from a circuit. It also has the advantage of a metal casing as one of the contacts, yet the casing 23 is a simple sleeve which is relatively easy to make.

The rod 21 may, if desired, be made in a. plurality of sections welded together end to end, with the section which passes through the glass wall 25h made of Kovar metal or metal having approximately the same thermal rate of expansion as the glass oi wall 25h. The section within the chamber of casing 23a. and slidingly an axis that is parallel to and offset from the Fig. 9, and function as explained in Figs. 1 to 8.

longitudinal axis of the switch, the mercury will move into a position along the wall which is farthest from the axis of rotation, but this zone may -be slightly ydiillerent, depending upon the original inclination of the axis of the switch, since gravity has a small influence in determining the position on the casing wall which the mercury globule will take when the switch is rotated. Since the head 28 is everywhere equidistant from the chamber wall along which the mercury can move, it follows that the extent of iiattening or distortion, which the globule of mercury must undergo to open the circuit will be the same regardless of the position in the casing of the globule at that time.

After a switch of the type shown in Figs. 1 to 6 is set, such as at the factory, to open the circuit at a given speed, no further adjustment of the device will be necessary when the position of the support of the device is changed, because the speed that will cause the circuit toy be opened will be the same in all positions of the switch, and the switch will close the circuit when idle in all angular positions in which it may be supported. It will be noted vthat the glass walls which close the metal casing are protected by metal, yet they give the samev advantages as a glass casing in the manufacture of a switch.

It will be understood that various changes in the details, materials, and arrangements ofparts,

which have been herein described and illustrated in order to explain the nature of the invention, may be made by those skilled in the art within the principle and scope of the invention as eX- e pressed in the appended claims.

I claim as my invention:

1. A mercury tube switch comprising a housing having therein a chamber, an electricity conducting element extending into said chamber and medium while resting on said enclosing wall, but

v separable from said member to electrically disprogressing along the surface of said chamber, an approximately sphere-like element also of electrically conducting material substantially smaller in diameter than the diameter'of said chamber disposed approximately centrally of said chamber and having its peripheral spherical surface exposed in said chamber, said medium and said element having electrically' conducting terminal terminating within the chamber in an exposed Y contact member spaced substantially everywhere approximately equidistant from the enclosing Y wall of said chamber, said housing having anex- `of is held away from and lagainst spreading along said enclosing wall, solely by its surface tension opposing the action of gravity thereon, and to touch said member and electrically connect it to said medium while resting on said enclosing wall, but separable from said member to electrically disconnect said member and said medium when said globule is distorted, through centrifugal extensions on the exterior of said chamber, and a globule of mercury within and only partially filling the space in said chamber between said element and the wall of said chamber, of a size which will assume a somewhat ball-like form by its surface tension acting against the force of gravity, and bridge the radial space between said element and said wall of said chamber and electrically connect said mediumy and said element, whereby when said body is rotated about an axis eccentric thereto, said globule will remain relatively motionless against a zone of said chamber wall but move therewith and by centrifugal forces undergo a change in its globular shape against the force of surface tension thereof, and by such change in shape to a Aselected extent, depending upon the centrifugal force acting on the globule, interrupt the circuit through the globule between said medium and said element.

Y 4. A mercury tube switch comprising a hollow casing of a `metal not wet `by mercury, said casing having an opening in its wall leading to the chamber therein, a wall of glass of approximately the same coefficient of thermal expansion as said metal, engaging and sealed to said casing entirely around said opening, an electrical conductor extending through said .glass wall into said chamber and within said chamber terminating in an exposed contact member spaced everywhere approximately equally from the enclosing wall of said casing, electrical leads to said casing and to the external end of said conductor, and a globforces acting thereon, by flattening against said enclosing wall against the action of its surface tension, while remaining undivided and in substantially the same relative position on said enclosing wall. A

2. A mercury tube switch comprising a housing having therein an approximately spherical chamber. an electricity conducting element extending into said chamber and having within the chamber an exposed contact member of generally spherical form spaced substantially everyi where approximately equidistant from theenclosing wall of said chamber, said housing having anexposed electricity conducting medium'progrossing along the major part of said enclosing wall, and avglobule of mercury within and only Partially lling the space in said chamber beule of mercury within and only partially filling the space in said chamber between said member and casing and of a size to assume a curved form in which a substantial portion thereof is held solely by its surface tension opposing gravity, away from and against spreading along the chamber wall of said casing and normally touching said member while resting on the chamber wall of said casing, but separable from said member to electrically disconnect said member and casing when said globule is distorted by flattening against4 said casing and against its surface tension while remaining undivided and in substantially the same relative position .on said wall.

5. A mercury tube switch comprising a hollow casing of a metal not wet by mercury, said casing having an opening in its wall leading to the chamber therein, a wall of glass of approximately the same coeiilcient of thermal expansion as said metal, engaging and sealed to said casing entirely around said opening, an electrical conductor extending through said glass wall into said chamber and within said chamber terminating in an exposed contact member spaced everywhere approximately equally from the enclosing wall of said is distorted by flattening against'sa'id casing and ber wall in opposition to its surface tension through centrifugal forces acting thereon, while it remains undivided and in substantially the same relative position on said chamber wall.

8. A mercury switch comprising a hollow casing of a metal not wet by mercury and which has a coefficient of thermal expansion that is approximately equal to that of a glass, closure means for against'its surface tension through centrifugal forces acting thereon, while remaining undivided and in substantially the same relative position on said wall, a metal ferrule surrounding said glass wall, electrically and physically connected to said casing, and a plastic medium filling said ferrule at the outer face of said glass and through which said electrical conductor extends and forms a terminal. f

6. A mercury switch comprising a hollow. spherically cup-like casing of a metal not wet by mercury. With the wall of said casing flanged outwardlyin a cylindrical manner at the mouth of the cup, a wall of glass of approximately the same coeicient of thermal expansion as said metal, closing the mouth of' said casing and having sealed therein the flanged wall of said casing, a conductor extending through said glass into the chamber ofsaid casing and within said chamber said casing and formed of said glass applied in sealing relation to an opening of said casing to close the chamber of said casing, a contact member extending through said glass closure means into said chamber vand within the chamber exposed for contact, a globule of mercury within and only partially filling said chamber and of a size to assume a curved form in which a substantial portion thereof is held solely by its surface tension opposing gravity away from and against spreading along the chamber wall, and normally touchingsaid contact member while resting von said casing wall but separable from said contact member within said chamber to electrically disconnect said head and casing when it is distorted by flattening against said casing in opposition to the surface tension of the globule through centrifugal forces acting thereon, while the globule remains undivided and in substantially the same relative position on the casing wall, and conducting means extending from said casing in insulated relation to said contact member.

9. A mercury switch comprising a hollow casing of a metal not Wet by mercury and which has a coeiiicient of thermal expansion that is approximately equal to that of a glass and a generally spherical chamber, closure means for said casing and formed of said glass applied in sealing relation to an opening of said casing to close the chamber of said casing, a contact member extending .through said glass closure means into said chamber and within the chamber having a ball-like head exposed for contact,

any part of the chamber wall dened by said casing, but separable from said head to electrically disconnect said head and casing when said lglobule is distorted by flattening Jof the same against said casing in opposition to the action of its surface tension through centrifugal forces acting thereon, while the globule remains undivided and in substantially thesame relative position on the casing wall exposed in said chamber.

7. A mercury switch comprising a hollow housing of insulating material, an electricity conductor extending through said housing into the chamber thereof and progressing somewhat spirally along the wall defining the chamber to the opposite side of the chamber, a contact member also extending through thehousing into said chamber spaced relatively to the said conductor and terminating within said chamber in a head having its exterior surface spaced approximately everywhere equidistant from the wall defining said chamber, and a globule of mercury within and only partially filling the space in said chamber between the said wall and said head, and of a size to assume a curved form in which a substantial portion thereof is held awayy from and against spreading along the chamber wall solely by its surface tension in opposition to the action of gravity thereon, and to touch saidhead while resting on said chamber wall and in contact with one of said spiral turns a globule of mercury within and only partially filling said chamber and of a size to assume a curved form in which a substantial portion thereof is held solely by its surface tension away from and against spreading along the chamber wall, and normally touching said contact member while resting on any part of said casing wall lbut separable from said contact member within said chamber to electrically disconnect said head and casing when it is distorted by flattening against said casing in opposition to the surface tensionl of the globule through centrifugal forces acting thereon, while the globule remains undivided and relatively immovable on the casing wall, and circuit connections to said casing and contact member. l

10. A mercury switch comprising a closed, hollow, generally spherical casing of a material not wet by mercury, and containing an inert atmosphere, a conductor` extending into the chamber of said casing and withinysaid cham-A ber terminating in a generally spherical head smaller than said chamber but spaced everywhere from said casing, a globule of mercury within and only partially filling the space within said chamber and of a size to assume a curved form in which a substantial portion thereof is held solely by its surface tension away from and against spreading along the chamber wall and normally touching said head while resting on any part of the chamber wall, but separable from said head to electrically disconnect it from said head and casing when said globule is distorted byfiattening of the same again.' said casing in opposition to the action of its surface low casing of a metalnot wet byl mercury, said casing having an opening in its wall leading to the chamber therein, a wall of glass of approximately the same ooefiicient of thermal expansion as said metal, engaging and sealed to said casing entirely around said opening, an dectrical conductor extending through said glass Wall into said chamber and within said chamber terminating in anexposed contact member spaced everywhere approximately equally from the enclosing wall of said casing, electricalleads to said casing and to the external end of said conductor, and a globule `of mercury within and only partially liing the space in said chamber between said member and casing and of a size to assume a curved form in which a substantial portion thereof is held solely by its surface tension opposing gravity, away from and against spreading along the chamber wall of said casing and normally touching said member while resting on .the chamber wall of said casing, but separable from said 4member to electrically disconnect said member and casing when said globule is distorted by flattening against said casing and against its surface tension through centrifugal forces acting thereon. while remaini undivided and in substantially the same relative position on said wall.

1,2. A mercury tube switch comprising' a housing having therein a closed switch chamber, an electricity conducting element extending yinto said chamber and having within the chamber. an exposed contactmember of generally similar form spaced substantially everywhere approximately equidistant from the enclosing wall of said chamber, said housing having' an exposed electricity conductor progressing in turns over the inner face of the major part of said enclosing wall, and a globule of mercury Within and only partially filling the space in said chamber between said enclosing wall and said member, said globule being of a size to assume a curved form in which a substantial portion thereof is heid away from and against spreading along said enclosing wall, solely by its surface tension opposing the action of gravity thereon, and to touch said member and electrically connect it to said conductor while resting on said enclosing wall, but separable from said member to electrically disconnect said' member and said conductor when said globule is. distorted; through centrifugal forces acting thereon, by iiattening against said enclosing wall against the action of its surface tension, while remaining undivided and in substantially the same relative posi- 4tion on said enclosing wall.

IIARRY L. LAMBERT. 

